1. Field of the Invention
The invention relates to a current-supply type monitoring system for the high-voltage supply of an ionization chamber, used preferably for the monitoring of particle accelerators.
2. Description of the Prior Art
It is known in the art of radiation systems of various types to switch them off via an ionization chamber to which the radiation is applied, as soon as a previously determined dosage of radiation has been applied. In the case of particle accelerators, it is furthermore known in the art to regulate the radiation intensity or output via the ionization current of an ionization chamber subjected to the radiation in such a way that the number of radiation impulses per unit time is changed in correspondence with the chamber signal measured. The transit time of ions produced within the ionization chambers is dependent on the spacing of the electrodes as well as on the voltage applied to the electrodes. Due to the limited life of the ions, their transit time within the chamber must be limited on the high side by decreasing the electron spacing and/or by increasing the voltage applied to the electrodes so that undesirably high losses due to recombination do not occur which would falsify the signal. The proportionality of the current flowing through the ionization chamber relating to the dosage output applied in the chamber remains constant while the supply voltage continues to increase until the electric field strength reaches a value at which the ions are accelerated to such an extent while traveling the average free path length dependent upon chamber pressure that they receive as much energy as is required for the ionization of other gas atoms. Ionization chambers are thus operated in this proportional voltage range since fluctuations of the supply voltage do not have an influence on the measured results. However, for very high dosage outputs as are present in the radiation impulses of particle accelerators or electron accelerators, considerable measurement inaccuracies have been found. This is a great disadvantage if the measured result is used for the control of accelerator intensity, i.e. for the regulation of the number of radiation impulses per time unit.